hugo-theme-hello-friend/source/css/archive.css

.archive {
  width: 100%;
  max-width: 800px;
  text-align: left;
  padding: 20px;
  margin: 0 auto;

  &__group {
    &-month {
      display: flex;
      align-items: flex-start;
      padding: 10px 0;

      @media (--phone) {
        flex-direction: column;
      }

      &:not(:last-of-type) {
        border-bottom: 1px solid var(--light-border-color);

        .dark-theme & {
          border-color: var(--dark-border-color);
        }
      }
    }

    &-year {
      margin-top: 40px;

      @media (--phone) {
        margin-top: 20px;
      }

      &:not(:last-of-type) {
        border-bottom: 1px solid var(--light-border-color);

        .dark-theme & {
          border-color: var(--dark-border-color);
        }
      }

      &-header {
        margin: 10px 0;
      }
    }

    &-month {
      &-header {
        margin: 25px 0;
        width: 200px;
        opacity: .5;

        @media (--phone) {
          margin: 10px 0 0;
        }
      }
    }

    &-posts {
      width: 100%;
    }
  }

  &__post {
    padding: 20px 0;

    &:not(:last-of-type) {
      border-bottom: 1px solid var(--light-border-color);

      .dark-theme & {
        border-color: var(--dark-border-color);
      }
    }

    &-title {
      margin: 5px 0;

      a {
        display: block;
        text-decoration: none;
      }
    }
  }
}